Fuel Misers

[Colin_P]

As a practical example, I wonder which driving method results on less fuel used in this case:

Downhill, followed by a similar uphill.

1) Use overrun downhill, travelling slower than if in neutral but using no fuel. Acceleration required to get car to top of uphill, thus using fuel

2) Coast car in neutral downhill. Faster than overrun but uses some fuel. Acceleration required to get car to top of hill but, due to greater speed at bottom of hill than overrun, less fuel needed to do this

Intuitively, (2) feels like it should be less..the tiny amount of fuel needed to keep the engine idling whilst coasting downhill being less than the additional fuel needed to get up the other side in overrun due to lower speed at bottom.of the hill

2, wins as you will need power to get up less of the hill. The amount of fuel used on an idling engine is negligable.


Again to those P&G sceptics which I once was, try it and report back.

 

[smutchin]

Again to those P&G sceptics which I once was, try it and report back.

It may well be more fuel efficient, but you've already set out a very good reason not to do it:

it can be really quite antisocial for other road users

 

[Drago]

So, does anyone here hyper mile, or at least drive lightly with an eye on their consumption?

 

[smutchin]

So, does anyone here hyper mile, or at least drive lightly with an eye on their consumption?

Fuel economy is a strong influence on my driving, but I don't do anything out of the ordinary - hadn't even heard of hyper-miling as a concept until today.

 

[DaveReading]

So, does anyone here hyper mile, or at least drive lightly with an eye on their consumption?

During the last fuel crisis I had to drive to the Northeast for a family funeral. With many petrol stations closed and the others rationing the amount they would sell you, I couldn't be sure that we'd get back home.

I resorted to driving without any shoes in an effort to make sure I had a light foot on the accelerator and it seemed to work as I got a good few extra mpg compared to a normal long run. We got as far as my sister-in-law's in Lincoln on the return journey before I abandoned the car, left the wife there and took the train back home.

 

[Drago]

The last fuel crisis was great. Quick flash of the warrant card, front of the queue

 

[BoldonLad]

Simple answer dont accelerate hard and lower your cruising speed and keep your tyres inflated

and, remove unnecessary clutter from the car/van.

 

[Drago]

Aye Mr Reiver. A grille block or tyres at max recommended pressure are one thing. Running tyres at 200psi and removing wiorrs and mirrors ismquote another.

 

[Profpointy]

I think it's

3) Accelerate in gear downhill to a speed that will then allow you to coast up the other side without needing to accelerate uphill

Of course the relative and absolute lengths of the uphill and downholl sections, and their gradients will affect this, but in theory it's best to gain all the kinetic energy when gravity is helping rather than when it's hindering.

My guess would be 3 as well, however whilst I'm pretty good on physics, it is an instinctive guess not a calculation

 

[BoldonLad]

[QUOTE 5111318, member: 9609"]Journey times are interesting too, if I drive back from my mothers (about 80 mile away) in the true style of a white van man I will get just 40 to the gallon and the journey will take me 1h45. Driving back with ecconomy in mind it will take me 2 hours but I can average 60mpg

so for an extra 15 minutes sitting in a warm vehicle listening to my music and not being stressed at needing to overtake the wagon in front I can save £3.80. (works out at £15 an hour for doing absolutely nothing)


heres a snap shot of my fuel use, can manage 800 mile for a full tank in the summer months
View attachment 390984 [/QUOTE]

I did not see in your table where the average speed was shown?

To AVERAGE 60mph, on an 80 mile journey, you have to go pretty fast, at certain times of the journey...

 

[gbb]

IME, coasting is definitely more efficient than engine braking in the following situations...
As said earlier, my commute was 21 miles of mostly quiet B roads, plenty of junctions and bends that required slowing and accelerating.
With coasting when appropriate up to junctions/ bends, i could coast for many hundreds of yards and my mpg was showing IRO 230mpg roughly.
If I'm in gear it'd be say 45 to 50 mpg just feathering the throttle. If I engine braked, I'd have to lift maybe 50 years from the junction, using no fuel.
Combine the two and only engine brake when I actually needed to slow quicker, i could regularly achieve 55 mpg In my former Astra 1.6 petrol. Without coasting id generally get 45 to 50 mpg. For many, 45 to 50 was good...for many more it was unachievable.
7 years of doing that and I found it quite consistent, costing is more economical.

As an indicator of driving style, the above used effectively, along with looking ahead and planning means you hardly touch the brakes and thinking about it, the last car I replaced pads on was probably my Lanci Beta...and that was around 30 years ago. Most of my cars are kept around 3 to 4 years and I genuinely can't remember fitting pads to a car after that....illl be generous and say maybe one car since, even so.

Habits of a lifetime...i spent years in a low paid job where every penny counted so I developed an efficient style out of neccessaty
. I don't need to now but it' so ingrained in me i cant help it.

 

[BoldonLad]

[QUOTE 5111318, member: 9609"]Journey times are interesting too, if I drive back from my mothers (about 80 mile away) in the true style of a white van man I will get just 40 to the gallon and the journey will take me 1h45. Driving back with ecconomy in mind it will take me 2 hours but I can average 60mpg

so for an extra 15 minutes sitting in a warm vehicle listening to my music and not being stressed at needing to overtake the wagon in front I can save £3.80. (works out at £15 an hour for doing absolutely nothing)


heres a snap shot of my fuel use, can manage 800 mile for a full tank in the summer months
View attachment 390984 [/QUOTE]

oops! my apologies @User9609, I miss-read your 60mpg as 60mph !

 

[swansonj]

It may well be more fuel efficient, but you've already set out a very good reason not to do it:

I respectfully dispute the term "antisocial".

Faced with a long hill, such as M40 northbound out of High Wycombe or the M40 "vicar of Dibley" hill southbound, I will gradually build my speed up to an indicated 75/actual 70 mph at the start. I will then choose a throttle opening that allows my speed gradually to drop to about 40mph by the top.

Going up the hill, no-one minds, because everyone accepts that people are allowed to go slowly up a hill. If, however , a lorry is just overtaking me at the top when my constant throttle opening results in acceleration again, they get really cheesed off.

I am unrepentant because I think that those of us who are antisocial enough to drive at all have a moral duty to drive as economically as possible.

Which is why I take the protestations of the haulage industry that they care deeply about fuel efficiency with a pinch of salt, when they drive everywhere on the speed limiter, maintaining 56 mph (or whatever) even up hills where it must be drinking fuel.

 

[Tin Pot]

I find the premium fuel is more economic/efficient.

I wait to find a steep incline on my route, slow down then, as I hit the base floor it and listen to the flat six singing as it soars over 6,000 rpm. Like a symphony of lions roaring against the existence of the universe.

Otherwise, it’s smooth acceleration, smooth braking, minimise sharp changes and hard braking. Leave it rolling up to the lights in case I can keep it moving as they change.

I hate the cars that accelerate towards red lights, or the back of a traffic queue.

 

[swansonj]

Also, a comment about drafting. You can get worthwhile improvements in economy at a distance behind a large HGV that is not stupidly close. Not as much, obviously, as if you do tuck up dangerously close behind, but still surprisingly worthwhile.